Research On Nonlinear Current-Voltage Characteristic Of MgTiO₃ Doped And Cu Non-stoichiometric CaCu₃Ti₄O₁₂ Thin Films

CaCu₃Ti₄O₁₂?CCTO?has attracted wide attention for its remarkable dielectric properties,it exhibits giant dielectric constant over 10⁴ in a wide temperature range of about 100⁴00K.The excellent dielectric properties of CCTO conform to the high integration of digital circuits and the miniaturization trend of electronic devices.CCTO also presents remarkable nonlinear I-V characteristics,resulting in the wide application in the field of microelectronics.In this thesis,the effects of MgTiO₃ doping and Cu non-stoichiometric ratio on the nonlinear I-V behavior of CCTO thin films were investigated,and a reasonable model was proposed to explain the experimental phenomena.CCTO ceramic target was prepared through the traditional solid-state method and the thin film was prepared through magnetron sputtering method in this thesis.The X-ray diffractometer was used to analyze the phase composition and field emission scanning electron microscope was used to observe the surface morphology of CCTO thin film and semiconductor parameter analyzer was used to investigate the I-V behavior of CCTO thin film.The I-V behavior of CCTO thin film was explained through Schottky emission model and Poole-Frenkel electronic transportation model based on the grain-grain boundary-grain structure of CCTO material,and Fowler-Nordheim tunneling model was used to explain the breakdown phenomenon.For the research of MgTiO₃ doping CCTO thin film,Cu²⁺and Ca²⁺in CCTO lattice were displaced by Mg²⁺as MgTiO₃ doping.The threshold voltage decreased with the increase of MgTiO₃ doping and temperature,and the Schottky barrier height increased firstly then decreased as MgTiO₃ doping while the trap energy level decreased monotonously.The nonlinear coefficient can get the maximum value of 3.799 when x=0.2.For the research of Cu non-stoichiometric thin film,CuO and TiO₂ were detected in all Cu-rich ceramic targets,and CuO was detected in thin film sample when x=0.8.Both Schottky emission and Poole-Frenkel electrons transportation process can be used to explain the nonlinear I-V behavior of CCTO thin films,and the Schottky barrier height increased monotonously as Cu content increase while the trap barrier height increased firstly then decreased.Nonlinear coefficient increased firstly and get the maximum value of 3.53 when x=0.4 then decreased.